Artificial cardiac pump

ABSTRACT

An artificial cardiac pump, comprising an impeller ( 3 ) rotatably supported on a fixed shaft body ( 2 ) in a housing ( 1 ) and a drive mechanism rotating the impeller, wherein blood is taken in from the front side and force-fed to the rear side by the rotation of the impeller ( 3 ). The shaft body ( 2 ) is connected between a front side fixed body ( 5 ) fixed to a straightening plate ( 4 ) joined to the housing ( 1 ) at the front of the impeller ( 3 ) and a rear side fixed body ( 7 ) fixed to a diffuser ( 6 ) joined to the housing ( 1 ) at the rear of the impeller ( 3 ). The impeller ( 3 ) further comprises a sleeve ( 8 ) having an inner peripheral surface opposed to the outer peripheral surface of the shaft body ( 2 ) through a minute clearance and front and rear end faces opposed to the rear end face of the front side fixed body ( 5 ) and the front end face of the rear side fixed body ( 7 ) through minute clearances, and an impeller ( 9 ) joined to the outer peripheral surface of the sleeve ( 8 ). The drive mechanism further comprises a polar anisotropical permanent magnet ( 10 ) enclosed in the sleeve ( 8 ) and a rotating field generator ( 11 ) enclosed in the housing ( 1 ).

FIELD OF THE INVENTION

The present invention relates to an artificial cardiac pump forforce-feeding blood as a substitute or an auxiliary of a heart of aliving body.

BACKGROUND OF THE INVENTION

In a conventional art, an artificial cardiac pump comprises a rotatableimpeller so as to be taken and force-fed blood. In general, artificialcardiac pumps can be divided into a group of axial-flow propeller pumpsand a group of rotary/centrifugal pumps. Upon comparing with the groupof the axial-low propeller pumps and the group of rotary/centrifugalpumps, the group of the axial-flow propeller pumps has an advantage inview of down-sizing. Hereinafter, it will be described an artificialcardiac pump with an axial-flow propeller pump.

For example, a conventional artificial cardiac pump comprises a rotorsuch as an impeller, wherein both ends of the rotor are rotatablysupported in a housing and a polar anisotropic permanent magnet isinstalled in the rotor, and a motor stator such as a rotary magneticflux generator, wherein the motor stator surrounds with a peripheral ofthe rotor and is installed in the housing. By magnetic co-relationbetween the polar anisotropic permanent magnet and the motor stator, therotor can be rotated with respect to the housing. Under such astructure, a characteristic of an artificial cardiac pump having atypically axial flow propeller pump can be obtained. That is, blood istaken from the front side and force-fed to the rear side by rotating theimpeller.

In the above conventional art, a rotor comprises a rotational axialmember of which the both sides are supported and impellerwing-components protruded from an outer peripheral surface of therotational axial member [i.e. Japanese Patent Publication 2001-523983(pages 23-26, FIGS. 4 and 9)]. Another rotor further comprises a shroudadjoined at an outer peripheral surface of the impeller and coaxiallylocated with respect to the rotational axial member [i.e. U.S. Pat. No.6,053,705]. In the former case, a polar anisotropic permanent magnet isinstalled in the rotational axial member. In the latter case, a polaranisotropic permanent magnet is installed in the shroud. In the formercase of the artificial cardiac pump, the shroud is unnecessary and astructure thereof can be simplified. Therefore, it is advantage in viewof down-sizing. On the other hand, in the latter case of the artificialcardiac pump, the anisotropic permanent magnet and the motor stator canbe alternatively and closely arranged. Therefore, it is advantage inview of a motor driving effort for rotating a rotor.

However, in the above described conventional artificial cardiac pumps,the both sides of the rotor are supported by fixed receiving parts ofthe housing in a contact relation. Thus, the both sides are worn downand burned. Such mechanical loss and damaes are occurred. In addition,blood is apt to be adhered/condensed around abraded powder as a core.Finally, a blood flwoing route such as blood vessel becomes narrower andthrombus would be occurred.

Concerning with such problems, the inventors provide an artificialcardiac pump having a housing in which a rotor is rotatably supported ina non-contact relation. An improved artificial cardiac pump provided bythe inventors will be described with reference to FIG. 3.

As shown in FIG. 3, the improved artificial cardiac pump comprises acylindrical housing 101, a rotor 103 rotatively supported in the housing101 in a non-contact relation, a plurality of board-shaped diffusercomponents 106 protruded from an inner wall of the housing 101 at a rearside with respect to the rotor 103, a rear side fixing body 107connected with an inner side edge of the diffuser 106 and an axial body102 fixed on a front end surface 107 a of the rear side fixing body 107.Thereby, a fixed axial body 102 is coaxially arranged with respect to acentral axis X′ in the housing 101.

The axial body 102 has an outer peripheral surface 102 a on which aninner peripheral surface 108 a of a sleeve 108 is circularly fitted. Thesleeve 108 is rotatably and movably supported with respect to the axialbody 102 along an axial direction. A plurality of impellerwing-components 109 are protruded from and fitted on an outer peripheralsurface of the sleeve 108. Further, at an outer edge of the impeller, acylindrical shroud 120 is coaxially fitted with respect to the sleeve108. The housing 101 includes a circular shroud receiving groove 101 ainto which the shroud 120 is installed. An inner wall of the circularshroud receiving groove 101 closely confronts with an outer peripheralsurface of the shroud 120. The rotor 103 is formed by the sleeve 108,the impeller 109 and the shroud 120.

Inside of the shroud 120, polar anisotropic permanent magnets 110 areradially arranged with respect to the central axis X′. At a front sidethereof, a ring-shaped shroud 120 is installed in the shroud 120. Thepolar anisotropic permanent magnets produce magnet flux perpendicular tothe outer peripheral surface of the shroud 120. The permanent magnet 110produces magnetic flux parallel to the outer peripheral surface of theshroud 120. On the other hand, in the housing 101 a motor stator 11 isarranged at a peripheral portion of a shroud receiving grooved portion101 a in order to surround with the shroud 120, wherein the motor stator111 comprises an electromagnetic coil for producing magnetic fluxtowards the outer peripheral surface of the shroud 120. In front of theshroud receiving groove portion 101 in the housing, a ring-shapedpermanent magnet 122 is installed so as to produce magnetic fluxperpendicular to the front end surface of the shroud 120.

In accordance with such an improved artificial cardiac pump, rotationalforce is transmitted to the polar anisotorpic permanent magnets 110 ofthe motor stator 111 by conducting electric current having differentphrases such as three phase electric current in an electro-magneticcoil. Thus, the sleeve 108, the impeller 109 and the shroud 120 of therotor are integrally rotated around the fixed axial body 102 in thehousing 101. Thereby, blood is sucked from the front side and taken intothe housing 101. The blood is pressurized by the impeller 109 and flowninto the diffuser 106. A hydrodynamic status is recovered to a staticstatus, while the blood is discharged to a rear side. In FIG. 3, a bloodflowing route is shown as white arrows.

A blood pressure level at a rear side (downstream) with respect to theimpeller 109 is higher than that at a front side thereof (upstream).Under the above structural condition, load is applied on the rotoritself along a direction from the rear side to the front side. As theresult, the front end surface of the shroud 120 is moved towards a frontend surface of the shroud receiving groove portion 101 a in the housing.However, repulsion force between the permanent magnets 121 and thepermanent magnet 122 is produced. Since the same magnetic polar arefaced each other. Thus, a contact/collision between the shroud 120 andthe housing 101 can be prevented. A part of high pressurized blood inthe rear side portion of the impellers 109 is flown to an end surface ofthe shroud receiving groove portion 101 a of the housing 101, a rearside surface of the shroud 120, an outer peripheral surface of theshroud 120 and a gap between the front end surface and the housing 101in order by utilizing a blood pressure difference. Thus, the bloodstream is joined to blood at the front side portion of the impellers109, that is, the blood taken into the housing 101.

The blood pressure difference as described above is utilized to supportthe rotor 103. That is, the sleeve 108 is supported with respect to theaxial body 102 in a non-contact relation. The part of the highpressurized blood at the rear side portion of the impeller 109 isintroduced to a micro gap between an outer peripheral surface 102 a ofthe axial body 102 and an inner peripheral surface 108 a of the sleeve108 from a back side with respect to the sleeve 108 through a gapbetween the front end surface 107 a of the rear fixed body 107 and therear end surface 108 c of the sleeve 108. Then, the blood is joined tothe blood taken into the housing by forwardly force-feeding the bloodthrough the micro gap. Accordingly, while the rotor 103 is rotating,blood is flown into the gap between the axial body 102 and the sleeve108 as lubricant fluid. The rotating rotor 103 is supported with respectto the axial body 102 in the non-contact relation.

As described above, in the above improved artificial cardiac pump, therotor 102 is supported and rotated in the housing 101 in the non-contactrelation so that mechanical loss (damage) and thrombus occurred in theconventional artificial cardiac pump of which a rotor is supported in acontact relation can be remarkably avoided.

However, the improved artificial cardiac pump as described abovecomprises a shroud 120 as one of components. Therefore, there arefollowing drawbacks. The shroud 120 is an outer-most wall of the rotorwith respect to a radial direction. At first, unless a weight balancecondition is even in the shroud 120, a dynamic balance of the rotorbecomes very large in a rotational condition. The rotor cannot berotated smoothly and such a situation is baneful for the non-contactrelation and the rotor would be makes vibrated. The shroud 120 is theouter-most wall of the rotor with respect to the radial direction.Mechanical loss and damage caused by rotating the rotor in blood cannotbe ignored. Particularly, the polar anisotropic permanent magnets 110that rotate the rotor 103 by confronting with the motor stator 111 isinstalled in the rotor. Therefore, a weight unbalance condition is aptto be occurred in the rotor, even if a degree of the weight unbalance isa little.

In the second, while the rotor 103 is rotated, blood is (reversely)flown into a gap between the shroud receiving groove portion 101 a andthe shroud 120 in the housing so that an efficiency of the pump isrestricted. If the gap between the shroud receiving grooved portion 101a and the shroud 120 becomes narrower so as to improve the efficiency ofthe pump, large shearing force is applied to blood flown therein.Because a peripheral rotational speed of the shroud 120 is higher thanthat of the shroud receiving grooved portion 101 a. The large shearingforce is depending on a rotational speed difference between the shroud120 and the shroud receiving grooved portion 101 a. Under the situation,an outer peripheral membrane of a number of red blood corpuscles aredamaged, so that a specific effect of the red blood corpuscle itself islost and blood is dissolved.

A purpose of the present invention is to resolve the above describeddrawbacks. An artificial cardiac pump according to the present inventioncan reduce the above mechanical loss based on a structure that animpeller is supported and rotated in a housing in a non-contact relationand improve pump efficiency.

THE DESCRIPTION OF THE INVENTION

To accomplish the above purpose, an artificial cardiac pump according tothe present invention comprises a housing, an impeller pivotallysupported with respect to an axial body fixed in the housing and adriving mechanism for rotating the impeller, wherein blood is taken infrom the front side of the impeller and force-fed to the rear side ofthe impeller along an axial direction by the impeller rotated by thedriving mechanism, the axial body is connected and sandwiched between afront side fixed body and a rear side fixed body, wherein the front sidefixed body is fixed at a straightening board protruded from an innerwall of the housing at a front side with respect to the impeller and therear side fixed body is fixed at a board-shaped diffuser protruded fromthe inner wall of the housing at a rear side with respect to theimpeller, the impeller comprises an inner peripheral surface confrontingwith an outer peripheral surface of the axial body with a micro gap, asleeve of which the both end surfaces confronting with a rear endsurface of the front side fixed body and a front end surface of the rearside fixed body with a micro gap, respectively and impellerwing-components protruded from an outer peripheral surface of thesleeve, and the driving mechanism comprises polar anisotropic permanentmagnets installed in the sleeve and rotary magnetic flux generatorinstalled in the housing and surrounding with a peripheral portion ofthe impeller.

Thereby, rotational force is applied to polar anisotropic permanentmagnets while a rotary magnetic flux generator is driven. By rotatingthe impeller, blood is taken into the housing from a front side of theimpeller and whirling blood is controlled through a straightening plateand pressurized to a hydrodynamic status by the impeller. The almostpart of the blood is recovered to a static status by the diffusers anddischarged to the rear side of the impeller. In such a case, a part ofhigh pressurized blood behind of the impeller is introduced into a microgap between a front end surface f a rear side fixed body and a rear endsurface of a sleeve. The blood is fed to the micro gap between the rearend surface of the front fixed body and the front end surface of thesleeve through a micro gap between an outer peripheral surface of theaxial body and an inner peripheral surface of the sleeve. As the result,the blood is join to the blood fed into the housing. Accordingly, whilethe impeller is rotating, blood as lubricant fluid is flown into microgaps formed between the sleeve and the rear end fixed body, the rear endfixed body and the axial body and the axial body and the front sidefixed body in order. Thus, while the impeller is rotating, radial loadthereof is supported by the axial body in a non-contact relation andthrust load is supported by the rear side fixed body and the front sidefixed body in a non-contact relation.

Further, the polar anisotropic permanent magnets for rotating theimpeller by confronting with a rotational magnetic flux generator aresurrounded with a sleeve as a component of the impeller. Therefore, thepump according to the present invention does not comprise a shroud thathas to be utilized in the conventional improved artificial cardiac pump.Accordingly, even if a weight unbalance condition is occurred at thesleeve located at an innermost location of the impeller with respect toa radial direction, baneful influence against the dynamic balance for arotating impeller is very little and the impeller does not vibrate somuch. An outer diameter of the impeller can be shortened and mechanicalloss and damages can be saved. In addition, blood reverse flow from theshroud that is often happened in the conventional improved artificialcardiac pump is completely resolved so that a pump efficiency can beimproved.

Therein, it is preferably to provide thrust hydrodynamic generatinggrooves for supporting thrust load of the impeller, wherein the thrusthydrodynamic generating grooves are provided at the rear end surface ofthe front side fixed body and the front end surface of the rear endfixed body. Those are confronting with the both end surface of thesleeve, respectively.

Further, while the impeller is rotating, load is applied on the impellerfrom a rear side to a front side due to blood pressure gap between thefront side and the rear side. Thereby, the front end surface of thesleeve is approached to the rear end surface of the front side fixedbody. If the front end surface of the sleeve is approached to the rearend surface of the front side fixed body very closely, the micro gapcannot be sufficiently provided. Under the condition, blood as lubricantfluid cannot be flown smoothly. If the gap becomes narrower, mechanicalloss and damages become serious and an amount of dissolved blood isincreased. In order to avoid the above problems, it is preferable toinstall a ring-shaped magnetic body confronting with an end surface ofthe sleeve at the rear end fixed body. Thereby, polar anisotropicpermanent magnets installed in a sleeve are drawn to a magnetic bodyinstalled in a rear side fixed body. An impeller is backwardly drawnagainst load caused by the blood pressure difference and applied towarda forward direction. Therefore, a front end surface of the sleeve is notapproached to a rear end surface of the front end fixed body veryclosely so that a micro gap can be certainly obtained.

The blood pressure difference produces load from a rear side to a frontside and the load is applied toward a rotating impeller so as to movethe front end surface of the sleeve to the rear end surface of the frontfixed body. If the front end surface of the sleeve moves toward the rearend surface of the front fixed body very closely, the micro gap cannotbe obtained sufficiently. The blood as lubricant fluid cannot be flownsmoothly. Further, the mechanical loss and damage become serious and anamount of dissolved blood are increased in the case that the micro gapcannot be maintained sufficiently. In order to avoid the above problems,a first magnet confronting with the rear end surface of the front endfixed body is installed in the sleeve and a second magnet confrontingwith the front end surface of the sleeve is installed in the front fixedbody, wherein the same polar of the first magnet and the second magnetare confronted each other so as to produce repulse force therebetween.The first magnet is installed in the sleeve and the second magnet isinstalled in the front fixed body. Thus the sleeve and the front fixedbody are repulsed each other. That is, the impeller is repulsedforwardly against load caused by the blood pressure difference andshifted to the front side thereof so that the front end surface of thesleeve is prevented from being approached to the rear end surface of thefront fixed body very closely and a micro gap can be certainly provided.

The above magnets are preferably permanent magnets. The permanentmagnets can maintain magnetic performance permanently so that amaintenance operation thereof can be omitted. The above magnets ispreferably a ring-shaped magnet of which an axial is coaxially with arotational axis of the impeller, respectively. Thereby, the impeller canbe rotated smoothly and the mechanical loss and damages can be reduced.

As described above, in accordance with the present invention, anartificial cardiac pump comprises a housing, an impeller rotatablysupported with respect to an axial body fixed in the housing and adriving mechanism for rotating the impeller, wherein blood is taken infrom the front side of the impeller and force-fed to the rear side ofthe impeller along an axial direction by the impeller rotated by thedriving mechanism, wherein the axial body connected and sandwichedbetween a front side fixed body and a rear side fixed body, wherein thefront side fixed body is fixed at a straightening board protruded froman inner wall of the housing at a front side with respect to theimpeller and the rear side fixed body is fixed at a board-shapeddiffuser protruded from the inner wall of the housing at the rear sidewith respect to the impeller, the impeller comprising an innerperipheral surface confronting with an outer peripheral surface of theaxial body with a micro gap, a sleeve of which the both end surfacesconfronting with a rear end surface of the front side fixed body and afront end surface of the rear side fixed body with a micro gap,respectively and impeller wing-components protruded from an outerperipheral surface of the sleeve, and the driving mechanism comprisingpolar anisotropic permanent magnets installed in the sleeve and rotarymagnetic flux generator installed in the housing and surrounding with aperipheral portion of the impeller. By rotating the impeller, blood issucked into the housing from the front side of the impeller and thewhirling component of the blood is controlled by passing though astraightening plate. Then, the blood is pressurized by passing throughthe impeller and introduced into a diffuser. In the diffuser, ahydrodynamic status is recovered to a static status while the blood isdischarge to the rear side of the impeller. The part of thehigh-pressurized blood behind the impeller is introduced into a microgap between the front end surface of the rear side fixed body and therear end surface of the sleeve. As the result, the blood is introducedinto a micro gap between the rear end surface of the front end fixedbody and the front end surface of the sleeve though a micro gap betweenan outer peripheral surface of the axial body and an inner peripheralsurface of the sleeve and then joined to blood in the housing. While theimpeller is rotating, blood as lubricant fluid is flown to the microgaps between the sleeve and the rear end fixed body, the rear end fixedbody and an axial body and the axial body and a front end fixed body inorder. At the rotating impeller, radial load with respect to theimpeller is supported by the axial body and thrust load with respect tothe impeller is supported by the rear side fixed body and the front sidefixed body in a non-contact relation.

In order to rotate the impeller, the polar anisotropic permanent magnetsconfronting with the rotary magnetic flux generator are installed in thesleeve as one of components of the impeller. Therefore, the artificialcardiac pump according to the present invention need not have a shroudutilized in a conventional artificial cardiac pump. Even if a weightunbalance condition is occurred at the sleeve located at the innermostportion of the impeller along the radius direction, baneful influencecaused by hydrodynamic unbalance can be saved with respect to theimpeller itself and its vibration can be also saved. Further, a lengthof an outer radius of the impeller can be shortened so that mechanicalloss and damages can be controlled. In addition, blood reversely flownto a shroud that is often happened in a conventional artificial cardiacpump is completely resolved so that an efficiency of the pump accordingto the present invention can be improved.

Trust hydrodynamic generation grooves for supporting thrust load appliedto the impeller are provided at the rear end surface of the front sidefixed body and the front end surface of the rear side fixed body whichare confronting each end surface of the sleeve. While the impeller isrotating, thrust hydrodynamic is produced at the micro gap formed by thesleeve, the front side fixed body and the rear side fixed body in bloodas lubricant fluid. Thus, the blood can be flown stably and the thrustload applied on the impeller is effectively supported.

In the case that a ring-shaped magnetic body for confronting with an endsurface of the sleeve is installed in the rear side fixed body, thepolar anisotropic permanent magnets installed in the sleeve are drawntoward the magnetic body installed in the rear side fixed body. That is,the impeller itself is drawn backwardly against load forwardly appliedcaused by a blood pressure difference. Under the condition, the frontend surface of the sleeve does not approach to the front end surface ofthe rear side fixed body too much so that it can be possible to providea micro gap in which blood as lubricant fluid is flown smoothly.

Further, the first magnet for confronting with the rear end surface ofthe rear side fixed body is installed in the sleeve. The second magnetfor confronting with the front end surface of the sleeve is installed inthe front side fixed body. The first magnet and the second magnet areinstalled so as to confront with the same polar of the first and secondmagnets and repulsion force is produced between the first magnet and thesecond magnet. Thus, the sleeve in which the first magnet is installedand the front side fixed body in which the second magnet is installedare repulsed each other. Under the condition, the front end surface ofthe sleeve does not approach to the front end surface of the rear sidefixed body too much so that it can be possible to provide a micro gap inwhich blood as lubricant fluid is flown smoothly.

In the case that the magnet is a permanent magnet, any maintenance formaintaining specific functions of the magnet is unnecessary. If themagnet is a ring-shape and arranged coaxially with a rotational axis ofthe impeller, the impeller can be rotated smoothly and mechanical lossand damaged can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross sectional view of one embodiment of an artificialcardiac pump according to the present invention.

FIG. 2 shows a plane view of a rear end surface of a front side fixedbody and a front end surface of a rear side fixed body for showingthrust hydrodynamic generation groove in one embodiment of an artificialcardiac pump according to the present invention.

FIG. 3 shows a vertical cross sectional view of a conventional improvedartificial cardiac pump.

FIG. 4 shows a vertical cross sectional view of another embodiment of anartificial cardiac pump according to the present invention.

THE BEST MODE OF THE INVENTION

In order to reduce mechanical loss and damages in an artificial cardiacpump with an axial pump and to improve efficiency thereof, the presentinventors have repeated structural experiments wherein an impeller isrotated in a housing in a non-contact relation. As the result, thepresent inventors paid attention to a shape of an impeller and theninvented the present invention. A main feature of the artificial cardiacpump according to the present invention is to omit a shroud that must berequired in a conventional improved artificial cardiac pump.

First Embodiment

An embodiment of an artificial cardiac pump according to the presentinvention will be described with reference to the accompanying drawings.FIG. 1 shows a vertical cross sectional view of an embodiment of anartificial cardiac pump according to the present invention. FIG. 2 showsa plan view of a rear end surface of a front side fixed body and a frontend surface of a rear side fixed body for showing thrust hydrodynamicgrooves in its artificial cardiac pump. In the drawings, the same namedcomponents indicates the same numerals, respectively. Therefore, thedescription thereof is omitted.

As shown in FIG. 1, the embodiment of the artificial cardiac pumpaccording to the present invention mainly comprises a cylindricalhousing 1, a fixed axial body 2 as a central axis X in the housing, arotor 3 that is an impeller rotatively supported in the housing withrespect to the axial body 2 and a driving mechanism for rotating therotor 3. By rotating the rotor 3, blood is taken from a front portion ofthe rotor 3 (right side in FIG. 1) and pressurized. Then, the blood isforce-fed to a back portion of the rotor 3 (left side in FIG. 1) alongan axial direction. In FIG. 1, a main blood route is indicated as whitearrows.

In the next, a detailed structure will be described. On an inner wall ofthe housing 1 located in front of the rotor 3, a plurality ofstraightening plate components are protruded and bonded as astraightening board 4. At an inner side of the straightening board 4, acylindrical front side fixed body 5 is coaxially arranged with respectto the central axis X and bonded. On the other hand, on an inner wall ofthe housing 1 behind the rotor 3, a plurality of board-shaped diffusercomponents are protruded and bonded as a diffuse 6. At an inner side ofthe diffuser 6, a cylindrical rear side fixed body 7 is coaxiallyarranged and bonded. A rear end surface 5 a of the rear side fixed body5 and a front end surface 7 a of the rear side fixed body 7 areconnected to the axial body 2. The axial body 2 can be fixed in thehousing 1. Therein, each central portion of a front end of the frontside fixed body 5 and a rear end of the rear side fixed body 7 isprotruded, respectively. The former protruded portion introduces suckedblood to distribute the straightening board 4 without any resistance.The latter protruded portion introduces blood flown from the diffuser 6so as to join the other blood without resistance.

On the axial body 2, a sleeve 8 is circularly fitted, wherein the sleeve8 includes an inner peripheral surface 8 a confronting with an outerperipheral surface 2 a of the axial body 2 with a micro gap, a front endsurface 8 b confronting with the rear end surface 5 a of the rear sidefixed body 5 with a micro gap and a rear end surface 8 c confrontingwith the front end surface 7 a of the rear side fixed body 8 with amicro gap. While the sleeve 8 is supported, the sleeve 8 is rotated withrespect to the axial body 2 and movable between the rear end surface 5 aof the front side fixed body 5 and the front end surface 7 a of the rearside fixed body 7. Further, on an outer peripheral surface of the sleeve8, a plurality of impeller wing-components 9 are protruded and bonded.Outer edge of the impeller is located close to an inner wall of thehousing 1. The rotor 3 comprises the sleeve 8 and the impeller 9.

Polar anisotropic permanent magnets 10 are radially arranged withrespect to the central axis X and installed in the sleeve 8. The polaranisotropic permanent magnets 10 produce magnet flux perpendicular tothe outer peripheral surface of the sleeve 8. On the other hand, a motorstator 11 formed by an electromagnetic coil for producing magnetic fluxperpendicular to the outer peripheral surface of the sleeve 8 surroundswith an peripheral portion of the sleeve 8 and is installed in thehousing 1. A driving mechanism for rotating the rotor 3 is formed by thepolar anisotropic permanent magnets 10 and the motor stator 11.

According to the artificial cardiac pump as described above, whileelectric current having different phases such as three phase electriccurrent is applied to the electromagnetic coil 3 of the motor stator 11,driving force (rotational force) for rotating the polar anisotropicpermanent magnets 10 is produced so that the sleeve 8 and the impellers9 of the rotor 3 are integrally rotated with respect to the fixed axialbody 2 of the housing 1. Thereby, blood sucked from the front side istaken into the housing 1 and the blood is flown through thestraightening plate 4 so as to control whirling movement. The blood ispressurized by impeller 9 and introduced to the diffuser 6 so that ahydrodynamic status is recovered to a static status and the blood isdischarged to the back side. Thus, as a fundamental function of anartificial cardiac pump, it is possible to force-feed blood under thepressure.

The pressure of the blood at the rear side (downstream) is higher thanthat at the front side (upstream) with respect to the impeller 9. A partof high-pressurized blood behind the impeller 9 is introduced to a microgap between the front end surface 7 a of the rear fixed body 7 and therear end surface 8 c of the sleeve 8. Then, the blood is fed to a microgap between the rear end surface 5 a of the front side fixed body 5 anda front end surface 8 b of the sleeve 8 through a micro gap between theouter peripheral surface 2 a of the axial body 2 and the innerperipheral surface 8 b of the sleeve 8. Accordingly, while the rotor 3is rotating, blood as lubricant fluid is flown to a gap between thesleeve 8 and the rear side fixed body 7, a gap between the rear sidefixed body 7 and the axial body 2 and a gap between the axial body 2 andthe front side fixed body 5 in order. At that time, radial load appliedto the rotor 3 is supported by the axial body 2 in a non-contactrelation and thrust load is supported by the rear side fixed body 7 andthe front side fixed body 5 in a non-contact relation.

The blood pressure difference as described above provides load onto therotating rotor 3 from the rear side to the front side. As the result,the front end surface 8 b of the sleeve 8 is approaching to the rear endsurface 5 a of the front side fixed body 5. If the front end surface 8 bapproaches to the rear end surface 5 a very closely, the micro gapbetween the front end surface 8 n of the sleeve 8 and the rear endsurface 5 a of the front side fixed body 5 cannot be maintainedsufficiently. The blood as lubricant fluid cannot be flown smoothly.Then, mechanical loss and damages are increased and an amount ofdissolved blood is increased.

Thus, in the embodiment according to the present invention, aring-shaped magnet 12 (such as iron plate and iron mass) arranged at alocation for confronting with the rear end surface 8 c of the sleeve 8is installed in the rear side fixed body 7. Thereby, the polaranisotropic permanent magnets 10 installed in the sleeve 8 are drawntoward the magnetic body 12 installed in the rear side fixed body 7.Accordingly, the rotor 3 is drawn backwardly against the load applied tothe front direction caused by the blood pressure difference. Therefore,the front end surface 8 b of the sleeve 8 is prevented from approachingto the rear end surface 5 a of the front side fixed body 5 very closely.A micro gap, in which blood as lubricant fluid is flown stably andsmoothly, can be provided certainly.

Further, the load forwardly applied caused by the blood pressuredifference or load suddenly varied along the central axis X in the casethat the artificial cardiac pump is energized and driven is applied asthrust load on the road. It may be baneful influenced to maintain themicro gap between the front end surface 8 b of the sleeve 8 and the rearend surface 5 a of the front side fixed body 5 and/or the micro gapbetween the rear end surface 8 c of the sleeve 8 and the front endsurface 7 a of the rear end fixed body 7.

As shown in FIG. 2, in the embodiment, a plurality of spiral shapedfront thrust hydrodynamic generation grooves 5 aa (6 grooves are shownin FIG. 2) are provided at the rear end surface 5 a of the front sidefixed body 5. The front thrust hydrodynamic generation grooves 5 aaapply thrust hydrodynamic to blood flown at a space between the grooves5 aa and the front end surface 8 b of the sleeve 8. Thereby, the thrustload applied forwardly can be supported in the rotor 3.

Likewise, a plurality of spiral rear side thrust hydrodynamic generationgrooves 7 aa are formed on the front end surface 7 a of the rear sidefixed body 7. The rear side thrust hydrodynamic grooves 7 aa applythrust hydrodynamic to blood flown at a space between the rear sidefixed body 7 and the rear end surface 8 c. Thereby, the thrust loadapplied backwardly can be supported in the rotor 3. Particularly, thethrust hydrodynamic is affected in the case of the magnetic body 12installed in the rear side fixed body 7. Such an effect is accomplishedimmediately after an excitation of the artificial cardiac pump. When therotor 3 is stopped, drawing force between the polar anisotropicpermanent magnets 10 and the magnetic body 21 is only produced in therotor 3. At the time, a contact relation between the rear end surface 8c of the sleeve 8 and the front end surface 7 a of the rear side fixedbody 7 is maintained. At the beginning, when the rotor is energized fromthis condition, the thrust hydrodynamic is immediately produced by takenin blood into a gap between the rear end surface 8 c of the sleeve 8 andthe front end surface 7 a of the rear side fixed body 7 so as to shiftin a non-contact relation.

Accordingly, when the rotor 3 is rotating, the thrust hydrodynamicpressure is occurred at micro spaces formed by the sleeve 8, the frontend fixed body 5 and the rear side fixed body 7 through blood aslubricant fluid. Thus, the blood can flow stably by certainly providingthese micro gaps and thrust load applied on the rotor 3 can beeffectively supported.

As described above, in the artificial cardiac pump according to thepresent invention, the polar anisotropic permanent magnets 10 forconfronting with the motor stator 11 are installed in the sleeve 8 as acomponent of the rotor in order to rotate the rotor 3. Therefore, it isunnecessary to provide a shroud 120 (see FIG. 3) utilized in aconventional improved artificial cardiac pump. Accordingly, even if aweight unbalance condition is occurred at the sleeve 8 located at aninner most portion of the rotor with respect to a radius direction,baneful influence for a dynamic balance of the rotating rotor 3 isreduced and a degree of a vibration of the rotor 3 is reduced. Further,a length of an outer diameter of the rotor can be shortened and themechanical loss and damages can be reduced. Further, happenings, whichblood is reversely flown to the shroud 120 utilized in the conventionalimproved artificial cardiac pump, are completely disappeared and itspump efficiency can be improved.

Upon comparing with the conventional improved artificial cardiac pumpand the pump according to the present invention, a relative distancebetween the polar anisotropic permanent magnets 10 and the motor stator11 is relatively large in the present invention. Although the motordriving efficiency becomes lower a little, rotational force applied tothe rotor 3 itself is not substantially influenced since an electriccurrent level and winding number of an electromagnetic coil are variedand the rotational force of the rotor 3 is controlled by coerecivity ofthe polar anisotropic permanent magnets 10.

Second Embodiment

In the next, the second embodiment of the artificial cardiac pumpaccording to the present invention will be described with reference tothe drawings. FIG. 4 shows a cross sectional view for showing astructure of the second embodiment of the artificial cardiac pumpaccording to the present invention. The embodiment is one of variationsmodified from the first embodiment as described above, wherein the samenamed components is numbered with the same reference numbers in thefirst embodiment of the artificial cardiac pump, respectively. Theexplanation thereof is omitted.

As shown in the drawings, the second embodiment of the artificialcardiac pump comprises a permanent magnet 13 as the first magnet and apermanent magnet 14 as the second magnet instead of the magnetic body12. The permanent magnet 13 is installed in the sleeve at which thepermanent magnet 13 is confronting with a rear end surface 5 a of afront side fixed body 5. The permanent magnet 14 is installed in thefront side fixed body 5 at which the permanent magnet 14 is confrontingwith a front end surface 8 b of the sleeve 8. The permanent magnets 13and 14 have a ring shape of which an axial is coaxially with arotational axis of the rotor (impellers) 3.

The both of the permanent magnets 13 and 14 produce magnet flux parallelto the central axis X. The same polar thereof are confronting each otherso as to produce repulsion force between the permanent magnet 13 and thepermanent magnet 14. Accordingly, the permanent magnets 13 and 14 have afunction as a thrust bearing along an axial direction of the centralaxis X. The rotor 3 is repulsed backwardly against the load caused bythe blood pressure difference and applied to a forward direction.Therefore, the front end surface 8 b of the sleeve 8 does not approachtoward the rear end surface 5 a of the front side fixed body 5 veryclosely so that a micro gap can be certainly provided so as to flowblood as lubricant fluid stably.

While the artificial cardiac pump is stopped or driven at a low speed,drawn force between the motor stator 11 and the polar anisotropicpermanent magnets 10 and repulsion force between the permanent magnet 13and the permanent magnet 14 make balance. Thus, the rotor 3 is moveddownwardly so as to prevent the rear end surface 8 c of the sleeve 8from contacting with the front end surface 7 a of the rear side fixedbody 7.

Regarding magnetic force of the permanent magnets 13 and 14, it ispreferable to note load applied forward by rotating the rotor 3.Depending on rotational speed of the rotor 3, a value of produced loadis varied. Judging from produced load corresponding to a rotationalspeed range of the rotor 3, the magnetic force is designed not tocontact the front end surface 8 b of the sleeve 8 with the rear endsurface 5 a of the front side fixed body 5 even if the maximum load isproduced. For example, even if the minimum load is produced, the frontend surface 8 c of the sleeve is designed not to contact with the frontend surface 7 a of the rear side fixed body 7. In the case of adjustingthe magnetic force, it may provide a magnetic body 12 employed in thefirst embodiment together with the permanent magnets 13 and 14 employedin the second embodiment.

The present invention is not restricted by any embodiments as describedabove. Various amendments may be acceptable unless a variation is withina scope of the present invention. For example, a cross sectional surfaceof the inner peripheral surface 8 a of the sleeve 8 is preferably acomplete circle. On the other hand, a cross sectional surface of theaxial body 2 is preferably an offset combination formed by twohalf-circles or four quarter-circles wherein a plurality of arc portionsare existed. In such a case, a micro gap between an outer peripheralsurface 2 a of the axial body 2 and an inner peripheral surface 8 a ofthe sleeve 8 can be certainly provided so as to flow blood as lubricantfluid smoothly. A shape of the front side thrust hydrodynamic generationgroove 5 aa and a shape of the rear side thrust hydrodynamic generationgroove 7 aa is not only spiral but also radial.

UTILITY IN THE INDUSTRY

The present invention relates to an artificial cardiac pump and isuseful as a substitute or an auxiliary of a heart of a living body.

1. An artificial cardiac pump comprising a housing, an impellerpivotally supported with respect to an axial body fixed in said housingand a driving mechanism for rotating said impeller, wherein blood istaken in from the front side of said impeller and force-fed to the rearside of said impeller along an axial direction by rotating said impellerby said driving mechanism; said axial body connected and sandwichedbetween a front side fixed body and a rear side fixed body, wherein saidfront side fixed body is fixed at a straightening board protruded froman inner wall of said housing at a front side with respect to saidimpeller and said rear side fixed body is fixed at a board-shapeddiffuser protruded from said inner wall of said housing at a rear sidewith respect to said impeller; said impeller comprising an innerperipheral surface confronting with an outer peripheral surface of saidaxial body with a micro gap, a sleeve of which the both end surfacesconfronting with a rear end surface of said front side fixed body and afront end surface of said rear side fixed body with a micro gap,respectively and impeller wing-components protruded from an outerperipheral surface of said sleeve; said artificial cardiac pumpcharacterized in that said driving mechanism comprises polar anisotropicpermanent magnets installed in said sleeve and rotary magnetic fluxgenerator installed in said housing and surrounding with a peripheralportion of said impeller.
 2. An artificial cardiac pump as claimed inclaim 1, characterized in that trust hydrodynamic generation grooves forsupporting thrust load applied to said impeller are provided at saidrear end surface of said front side fixed body and said front endsurface of said rear side fixed body which is confronting with each endsurface of said sleeve, respectively.
 3. An artificial cardiac pump asclaimed in claim 1, characterized in that a ring-shaped magnetic bodyfor confronting with an end surface of said sleeve is installed in saidrear side fixed body.
 4. An artificial cardiac pump as claimed in claim1, characterized in that a first magnet for confronting with said rearend surface of said rear side fixed body is installed in said sleeve; asecond magnet for confronting with said front end surface of said sleeveis installed in said front side fixed body; wherein said first magnetand the second magnet are installed so as to confront with the samepolar of said first and second magnets and repulsion force is producedbetween said first magnet and said second magnet.
 5. An artificialcardiac pump as claimed in claim 4, characterized in that said magnet isa permanent magnet.
 6. An artificial cardiac pump as claimed in claim 4,characterized in that said magnet is a ring-shape and arranged coaxiallywith a rotational axis of said impeller.
 7. An artificial cardiac pumpas claimed in claim 2, characterized in that a ring-shaped magnetic bodyfor confronting with an end surface of said sleeve is installed in saidrear side fixed body.
 8. An artificial cardiac pump as claimed in claim2, characterized in that a first magnet for confronting with said rearend surface of said rear side fixed body is installed in said sleeve; asecond magnet for confronting with said front end surface of said sleeveis installed in said front side fixed body; wherein said first magnetand the second magnet are installed so as to confront with the samepolar of said first and second magnets and repulsion force is producedbetween said first magnet and said second magnet.
 9. An artificialcardiac pump as claimed in claim 3, characterized in that a first magnetfor confronting with said rear end surface of said rear side fixed bodyis installed in said sleeve; a second magnet for confronting with saidfront end surface of said sleeve is installed in said front side fixedbody; wherein said first magnet and the second magnet are installed soas to confront with the same polar of said first and second magnets andrepulsion force is produced between said first magnet and said secondmagnet.
 10. An artificial cardiac pump as claimed in claim 7,characterized in that a first magnet for confronting with said rear endsurface of said rear side fixed body is installed in said sleeve; asecond magnet for confronting with said front end surface of said sleeveis installed in said front side fixed body; wherein said first magnetand the second magnet are installed so as to confront with the samepolar of said first and second magnets and repulsion force is producedbetween said first magnet and said second magnet.
 11. An artificialcardiac pump as claimed in claim 8, characterized in that said magnet isa permanent magnet.
 12. An artificial cardiac pump as claimed in claim9, characterized in that said magnet is a permanent magnet.
 13. Anartificial cardiac pump as claimed in claim 10, characterized in thatsaid magnet is a permanent magnet.
 14. An artificial cardiac pump asclaimed in claim 8, characterized in that said magnet is a ring-shapeand arranged coaxially with a rotational axis of said impeller.
 15. Anartificial cardiac pump as claimed in claim 9, characterized in thatsaid magnet is a ring-shape and arranged coaxially with a rotationalaxis of said impeller.
 16. An artificial cardiac pump as claimed inclaim 10, characterized in that said magnet is a ring-shape and arrangedcoaxially with a rotational axis of said impeller.
 17. An artificialcardiac pump as claimed in claim 11, characterized in that said magnetis a ring-shape and arranged coaxially with a rotational axis of saidimpeller.
 18. An artificial cardiac pump as claimed in claim 12,characterized in that said magnet is a ring-shape and arranged coaxiallywith a rotational axis of said impeller.
 19. An artificial cardiac pumpas claimed in claim 13, characterized in that said magnet is aring-shape and arranged coaxially with a rotational axis of saidimpeller.